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  1. #include <iostream>
  2. #include <ctime>
  3.  
  4. bool IsPalindrome( int n )
  5. {
  6.   int nCpy = n;         // Copy of n
  7.   unsigned long r = 0;  // n reverse
  8.  
  9.   while( nCpy > 0 )
  10.   {
  11.     r = r * 10 + nCpy % 10;
  12.     nCpy /= 10;
  13.   }
  14.  
  15.   return n == r;
  16. }
  17.  
  18. int main( int argc, char* argv[] )
  19. {
  20.   unsigned long largest = 0;  // Largest palindrome
  21.   unsigned int i, j;          // Loop counters
  22.   unsigned long p;            // Product of i and j
  23.   int first, second;          // Factors
  24.   clock_t t = clock();        // Timer
  25.  
  26.   for( i=100; i < 1000; ++i )
  27.   {
  28.     for( j=100; j < 1000; ++j )
  29.     {
  30.       p = i * j;
  31.       if( IsPalindrome( p ) )
  32.       {
  33.         if( p > largest )
  34.         {
  35.           largest = p;
  36.           first   = i;
  37.           second  = j;
  38.         }
  39.       }
  40.     }
  41.   }
  42.  
  43.   t = clock() - t;
  44.   std::cout << "The largest palindrome is " << largest;
  45.   std::cout << " (" << first << " x " << second << ")\n";
  46.   std::cout << "Time taken: " << static_cast<float>( t ) / CLOCKS_PER_SEC << " seconds\n";
  47.  
  48.   return 0;
  49. }
Success #stdin #stdout 0.02s 2852KB
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Standard input is empty
stdout
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The largest palindrome is 906609 (913 x 993)
Time taken: 0.02 seconds
https://ideone.com/zQBwpD
language:
C++ (gcc 8.3)
created:
12 years ago
visibility:
public

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